In a silver halide photographic material, a photosensitive layer or another layer is sometimes dyed or otherwise colored to insure selective absorption of light in a definite wavelength region.
Light passing through the photosensitive and other layers is sometimes scattered by the silver halide grains, etc. present in the layers or reflected by the interface between the photosensitive layer and the support and/or between the photosensitive layer and the layer disposed on the opposite side and re-enters the photosensitive layer to sensitize the emulsion and form an image in a position shifted from the original position of light incidence. This results in the whole image being blurred or diffused. Also an object of coloring a photosensitive layer is to preclude the above result.
Particularly in a photosensitive material such as a color printing paper wherein a reflective support is employed, the support itself has strong reflectivity to a certain limited degree so that, on exposure, light not absorbed by the photosensitive and other layers tends to be reflected in random directions with high probability and enters the photosensitive layer to sensitize the emulsion and form images in diffused positions other than the proper position of the image formed by incident light. Therefore, in such a photosensitive material, it is a known and common practice to inhibit this image blurring or bleeding by incorporating an appropriate dye in a hydrophilic colloid layer of the material.
On the other hand, another known and important factor in the prevention of image blurring or bleeding is prevention of scattering of incident light by the silver halide grains themselves which are present in the photosensitive layer. The question of the scattering of light by silver halide grains, in addition to its characteristics in photosensitive layers, has been discussed in Mees & James, The Theory of the Photographic Process, Fourth Edition, (1966) pages 580-590. Notwithstanding the descriptions in this and other textbooks, it is well known to those skilled in the art that it is advantageous to minimize the coating amount of silver halide grains in the photosensitive layer and since the light scattering characteristics are related to the size of silver halide grains and the wavelength of light, it is advantageous to avoid as much as possible a grain size and a grain size distribution disadvantageous form the standpoint of light scattering. More recently, as disclosed in U.S. Pat. Nos. 4,434,226, 4,439,520, 4,433,048, 4,386,156, 4,399,215 and 4,400,463, etc., use of tabular silver halide grains oriented in parallel with the plane of the photosensitive layer to thereby reduce the irradiation taking place in the photosensitive layer of the silver halide photographic material to a substantial extent has been proposed and, hence, to improve the sharpness of the reproduced image.
Even in a silver halide photosensitive material having a reflective support, too, the light incident on the surface of its photosensitive layer is similarly scattered by the silver halide grains in the photosensitive layer to yield a blurred image with reduced sharpness. Therefore, it appears equally advantageous, even in such a silver halide photosensitive material having a reflective support, to minimize the coating amount of silver halide grains in the photosensitive layer or, on considering light scattering characteristics in relation to the grain size of the silver halide and the wavelength of light, to avoid as much as possible a grain size and a size distribution being disadvantageous from the standpoint of light scattering.
To meet the current demand for rapid processing in the field of photographic materials and/or for low replenishment, efforts are being made to respond to this demand by reducing the coverage of a silver halide emulsion as a photosensitive layer. Such efforts should give rise to advantageous in improving image sharpness.
However, it has been discovered that this is not necessarily true with a silver halide photosensitive material having a reflective support. Thus, it was found that reducing the coating amount of silver halide emulsions in such a material may rather result in decreased sharpness. Therefore, it is important to prevent deterioration of sharpness in such a system and it is important not only to meet the requirements for rapid processing and low replenishment by reducing the coating amount of the silver halide emulsion but also to implement a reduction in production cost by reducing the consumption of silver.